Facsimile has become a widespread and ubiquitous technology over the past few years. Facsimile transmissions rely upon an image at one facsimile machine being translated into a sequence of tones, transmitted over the telephone network, and received by a receiving facsimile machine. The receiving facsimile machine then reconstructs the original image from the tones.
Of course, in order for the receiving and transmitting facsimile machines to properly work together, there must be a protocol agreed upon in advance. More specifically, the receiving facsimile machine must be aware of the encoding scheme used to convert the image into tones. Additionally, the receiving and transmitting facsimile machines must agree upon timing, maximum delays, etc.
There are a small number of worldwide standards that are used by facsimile machines in order to permit nearly any transmitting facsimile machine and any receiving facsimile machine to work together. Part of the protocol utilized by the facsimile machines involves timing the transmission of the tones correctly. The timing requirements however, are difficult to meet with facsimile systems which operate over data networks because the original protocols were designed to operate over a telephone network. The protocols therefore, are all designed with the presumption that there is a dedicated circuit connection between the transmitting and receiving facsimile machine.
The dedicated circuit introduces a relatively constant and extremely minimal transmission delay. The standardized facsimile protocols are therefore designed to operate within the worst case delay typically introduced by a dedicated circuit.
One such protocol which has gained widespread acceptance is termed the T.30 protocol. The T.30 protocol has been adapted by the International Telecommunications Unit, has been in widespread use for many years, and is implemented by nearly all facsimile machines in the world.
Recently, it has become more common to transmit facsimile images over data networks such as Local Area Networks (LANS) and Wide Area Networks (WANS). As transmission of facsimile images over data networks such as the Internet has become more prevalent, timing problems have become a major issue. For example, when facsimile images are transmitted over the Internet, variable and often unpredictable delays are introduced. The image to be transmitted is broken down into data packets which may arrive at different times and experience different delays as they are transmitted from node to node through the Internet. These variable and unpredictable delays often result in transmission timing which is outside the requirements of the facsimile protocol being implemented between the transmitting and receiving facsimile machine. As a result, the receiving facsimile machine may simply hang up, believing that there was a transmission error when in fact there was only a short delay.
One major reason for the timing problems which arise when transmitting facsimile images over the Internet is that the traffic load being handled by the various internet nodes varies in a dynamic and often unpredictable manner. Moreover, the routing tables utilized by the Internet do not vary, so that as a node becomes more heavily loaded, all communications involving that node slow down. The following example will help clarify.
Consider the arrangement shown in FIG. 2 comprising a plurality of Internet nodes 201 through 206. Each node 201-206 includes a routing table utilized to route data from the node to any other node. The routing tables are constructed based upon an established path between nodes. The established path is determined by a central location in accordance with well known techniques.
The routing table only instructs the node to route the data to the next node in the path. Thus, consider an established path from node 201 to node 204 through nodes 202 and 203. The routing table in node 201 provides that data destined for node 204 be transmitted to node 202. The routing table in node 202 provides that the data destined for node 204 be routed to node 203, and the routing table in node 203 then routes the data to node 204.
The problem arises when node 202, for example, begins to become heavily loaded with traffic, and thus packets traveling through node 202 experience large delays. The delay may be caused by other packets which are being routed, through node 202, between other nodes. The delays may fall outside of the restrictions of the T.30 protocol.
One prior art solution to the above problem is to provide storage facilities in the Internet service provider for transmitting the facsimile image utilizing a store and forward technique. Such an arrangement is shown in FIG. 1.
In operation, when it is desired to transmit a facsimile image from facsimile machine 101 to facsimile machine 102, the facsimile is first sent from facsimile machine 101 to facsimile storage device 105. The facsimile machine 101 can not distinguish between facsimile storage device 105 and a typical facsimile machine. Moreover, connection 110 is a standard telephone connection so that the communication between facsimile machine 101 and facsimile storage device 105, over connection 110, can operate in accordance with the standard facsimile protocols designed for a circuit switched connection.
After the image is stored at facsimile storage device 105, it is transmitted, via internet interfaces 106 and 107, over the Internet to facsimile storage device 108 using standard Internet protocols (e.g.; TCP.backslash.IP) which do not depend upon critical timing requirements set forth in the standard facsimile protocols. Next, the image is sent from facsimile storage device 108, to facsimile machine 102 via a standard facsimile connection over telephone line 111. The image may then be transferred in real time, in accordance with standard techniques, over telephone line 111.
The techniques set forth in FIG. 1 are acceptable but not ideal. One problem is that the facsimile image is not transmitted in real time. Specifically, when a user of the facsimile machine 101 is finished sending the facsimile, the user of facsimile machine 102 does not have it. Rather, the image is simply stored at facsimile storage device 105. For the image to be transmitted from Interface 106 to Interface 107, and then on to facsimile machine 102, may take several minutes or even hours. Thus, one of the main advantages of facsimile technology, the ability to have documents sent from one place to another instantly, is lost. As a result, the user of facsimile machine 101 can not be assured that the transmission is received at the other end just because he is finished sending it.
There exists a need in the art to provide a system for real time facsimile transmission over the Internet which solves the problem of the transmission delay introduced by the Internet causing delays that fall outside the scope of acceptable facsimile protocols.